1. Field of the Invention
The present invention relates to a guest-host liquid crystal display device having tilted-homeotropic orientation which include a nematic liquid crystal or a mixed nematic liquid crystal having negative dielectric anisotropy with a dichroic dye.
2. Description of the Prior Art
The guest-host liquid crystal display device is formed by holding a liquid crystal with a dichroic dye between a pair of electrode plates in orientation and changes its display color by varying the orientation of the liquid crystal and the dichroic dye by turning on and off. Various studies for research and development have been made in view of advantageous characteristics of capability of various color displays and broad sight.
In the guest-host liquid crystal display device in which the nematic liquid crystal or the mixed nematic liquid crystal having negative dielectric anisotropy is used as the host and the dichroic dye is used as the guest, it is preferable to attain the orientation treatment so as to maintain less than 10 degree of an angle .theta..sub.1 of the orientation of the liquid crystal molecules (2) to the normal direction h on the electrode surface (1) as shown in FIG. 1 in order to increase the contrast ratio by using a polar film. It has been reported to be necessary to provide the shape anisotropy by the oblique evaporation on the surface of the electrode plates which are overcoated and further the orientation treatment with a surfactant giving homeotropic orientation in order to attain such tilted-homeotropic orientation as disclosed in The 24th Japan Applied Physics Conference Pretext 29a-G-3, 1976 by Wada et al. In the oblique evaporation, it is, however, necessary to deposite it at a large angle as about 85 degree of the angle .theta..sub.2 to the normal direction h on the electrode surface (1) as shown in FIG. 2 by using SiO as a depositing material. Moreover, an allowable thickness of a deposited layer is quite narrow range as about 50 to 120 A, to be remarkably inconvenient in the practical use. In such evaporation and the condition of the evaporation, it is difficult to treat a plate having a large area. It is also difficult to attain a mass production. Therefore, the cost is high. As described above, there are various industrial disadvantages to attain the tilted-homeotropic orientation by the surface treatment on the oblique evaporation layer.